1. Field of the Invention
The present invention relates to a communication apparatus that is employed for a multi-media network, etc., and in particular to a communication apparatus that performs the accounting for a communication service for encrypted secret information; and to a communication system that employs such a communication apparatus.
2. Related Background Art
Recently, in consonance with the preparation of optical fiber networks for trunk communication networks, the spread of cable television systems, the practical use of satellite communications, and the spread of local area networks, there has been an expansion of the so-called information service industry that provides various information, across a communication network, such as images, sounds, and computer data, and charges service fees in consonance with the contents and the amount of the information that is provided. It is important that such services have means to properly account for provided information.
However, in many cases conventional accounting systems are monthly systems, such as those for cable television systems or broadcast satellite systems, that are not concerned with the frequency of service, or accounting systems, such as for computer services, that count only the service frequency (or service time) and that are not concerned with the types or quality of provided information.
It is vitally important that information transmission across a communication network be secure, and various systems for enciphering information and transmitting the enciphered information have been proposed as secure transmission means.
When an information service uses a conventional enciphering system to keep information secret, however, the conventional enciphering system will not be able to cope with the various types of information and services as they continue to expand in the future.
It is assumed that generally an information providing center can provide not only one type of information, but that it can provide an assortment of different types of information. The various types of information differ in their worth, however, and accordingly, conditions wherein the information providing center calculates a charge should be different. From the view of the amount of information that is to be provided, since the quantity of data that is required for an animated image is considerably greater than the data that is required for text information, with an accounting system according to which charges are based on the quantity of information dispensed, a user that received animated image information would have to pay a fee that was a multiple times of the service fee charged for text information. Such an accounting system would be unrealistic.
The conventional accounting system for an information service has the above described problems.